This invention relates generally to the field of powerline management, and, more particularly to a new approach that directly determines temperature of an overhead electrical conductor at time of 3-dimensional location data collection, for use in such applications as CAD modeling of the conductor, thermal line analysis of the conductor, thermal rating of a power line that includes the conductor, clearance analysis relative to the conductor, vegetation management relative to the conductor, and/or other applications especially useful to electric utilities in safeguarding and optimizing their transmission and distribution infrastructure.
LiDAR (Light Detection And Ranging) is used to produce CAD (Computer Assisted Design) models of powerlines. In the process known to industry, LiDAR data is collected using a sensor that is mounted to an aerial platform, tripod or a land vehicle. For clearance analysis during different conductor conditions, it is important to know the temperature at the time the LiDAR data was collected. In the process known to industry, LiDAR data is captured simultaneously with weather and line loading data that allows modeling the conductor temperature.
The process of predicting conductor temperature at time of LiDAR data collection using loading and weather data requires accurate knowledge of weather conditions at the right-of-way. Especially, prediction of wind speed and direction are difficult to perform due to turbulence and high variation of wind speeds. Weather stations have to be employed to acquire the weather information.
The U.S. government is currently mandating modernization of the nation's electrical grid in order to enhance national security. As part of this effort, the North American Electric Reliability Corporation (NERC)—certified by the Federal Energy Regulatory Commission to develop and enforce reliability standards for the electric grid in North America—on Oct. 7, 2010 issued a regulatory alert requiring all transmission line operators to assess within the next three years the precise physical characteristics of their high voltage transmission lines relative to design specifications. NERC recommended that utilities use PLS-CADD (engineering software that determines what the wire's physical properties and where the conductor is located under given conditions, based on temperature and conductor type inputs) to comply with this requirement. The actual conductor temperature will be a leading indicator for NERC.
Current industry practice calculates—rather than measures—the temperature of a bare conductor, utilizing factors such as ambient weather conditions, physical and thermal properties of the conductor, and line loading information. Due primarily to weather variables, this practice can generate a significant margin of error. The associated uncertainty of a conductor's temperature directly limits its capacity.
The power conductors of overhead transmission lines are self-supporting and energized at high voltage. As current flow through conductors increases, the temperature of the conductors increases, causing them to elongate. This elongation increases the sag of the conductors between support points, decreasing the clearance between the conductors and people, the ground, vegetation, buildings and vehicles under the lines. Beyond certain “maximum allowable” sag, the lines may flashover, resulting in either a power supply outage or injury to the public. Additionally, if conductor temperature remains high for an extended period of time, the strength of the conductors and tensioned connectors may decrease, which could trigger mechanical failure during the next occurrence of ice or high wind loading. To avoid excessive sag or loss of strength, limits are placed on maximum operating temperature of the conductor.